Two-cycle engine



Dec. 8, 1936. G. EXEL 2,053,665

TWO-CYCLE ENGINE Filed Oct. 4, 1935 2 Sheets-Sheet I I I III l l l l l l l l l l l l 15 Illlllllll ATTORNEY.

G. EXEL TWO-CYCLE ENGINE Filed Oct. 4, 1935 Dec. 8, 1936.

. Gauge 2 Sheets-Sheea INVENTOR, Egel, K

ATTORNEY.

Patented Dec. 8, 1936 UNITED STATES PAT-Ear orrics 7 Claims.

It has been proposed to provide a two-cycle internal-combustion engine characterized by a fixed piston and a cylindrical moving or power piston containing the fixed piston and contained by the cylinder of the engine, the construction being such that each charge admitted to the space between the fixed and power pistons is bypassed, upon compression thereby and at the end of each stroke of the power piston for effecting such compression, to the combustion chamber or space between the power piston and cylinder head. The object of this invention is to increase the efiiciency of engines of this class in these respects, to wit: By making it possible to increase the displacement of the fixed piston without sacrifice of the strength or durability of so much of the movable system of the engine as directly includes the power piston; by providing for regulating at will the degree of the primary compression; and by providing means which will avoid the losses in compression which have heretofore been incident to the operation of engines of this class.

In the drawings,

Fig. 1 is a view, partly in elevation and partly in vertical section in a plane coincident with the crank-shaft, of one form of an engine embodying the invention;

Fig. 2 is a fragmentary elevation, viewed from the right in Fig. 1, of the power piston and its sleeve;

Figs. 3 and 4 are sections on lines 3--3 and 44, Fig. 1;

Fig. 5 is a view similar to Fig. 1 showing another form of the engine;

Fig. 6 is a plan, partly in section, of the disk upon which the fixed piston structure is mounted;

Fig. '7 is a plan of the plate 40 with said disk removed;

Fig. 8 is a fragmentary view showing the disk and one of the standards for the fixedpiston in section on line 88, Fig. 6, and another such standard in elevation, and

Fig. 9 shows a modified form of the power piston structure.

Referring, first, to Figs. 1 to 4:

On the crank-case I, in which is journaled the crank-shaft 2 having connected with its crank the piston-rod 3, in turn oscillatory on the shaft 4, is bolted the cylinder 5 with a plate 6 intervening between them, said cylinder being closed at the top and open at the bottom.

Within the cylinder but spaced therefrom is the fixed piston 1 provided with piston rings 8 and supported by the standards 9 (four in number) which are in turn supported by the disk 6, the disk, piston and standards being suitably secured together rigidly. To permit the piston-rod to partake of the rotary motion of the crankshaft crank to which it is connected, the disk has a slot 6a.

Within the cylinder and receiving the fixed piston is the power piston structure including three main parts and constructed as follows:

The body I!) of this piston includes a closed head or actual piston and a depending cylindrical skirt into which the fixed piston snugly fits. The skirt is connected at its lower end with the piston rod, thus: In an engine of this class it is known that the more the displacement of the fixed piston approximates that of the power piston the greater is the efficiency developed. To this end I am able to reduce the thickness of the power piston skirt and at the same time produce a substantial connection between the power piston and the means through which it drives the crankshaft 2 by providing a collar H which is formed separately from the skirt and is attached thereto, as by screwing it into the same; in the example the collar receives the pin 4, being preferably thickened up, as at Ha, for that purpose. Preferably some of the thrust of the pin is assumed by the skirt and the body I0 is kept from turning on the collar (with consequent failure of cooperation of the ports of the power piston and cylinder) by causing the pin ends to enter holes i2 formed in the skirt, the shaft being held against endwise displacement and the consequent danger of scoring the cylinder by cotter-pins I3 engaging the bosses ila. In previous engines of this class the shaft has been connected directly to the skirt. If the head and skirt of the body were desirably formed integral there was then no recourse (in view of the presence of the fixed piston) but to form the skirt as a whole thick enough to withstand the thrusts of the pistonrod, with a consequent obvious limiting of the eficiency possible. Besides the body Ill and collar l l the power piston includes a split-sleeve which is here formed in two sections l4a-| lb one of which, as I la, is of greater circumferential extent than the other, and elastic expansion rings l5 occupying inside circumferential grooves, as shown, in the sleeve. The body is provided with upper and lower sets of piston rings l6 and from a shoulder ltd thereof near its base to the upper set of these rings it is of reduced exterior diameter and the sleeve and its rings occupy the space thus formed between the body and the cylinder, the former fitting between the upper set of rings l6 and said shoulder and being held in circumferential sealing relation to the cylinder by its own rings. The sleeve is held against rotation with respect to the piston body by a lug ll engaging in notches formed in both sections of the sleeve.

The body ll], usually formed of cast-iron, may be reinforced by an embracing steel band lea: shrunk thereon at its lower end, Fig. 9. Here the band opposes the ends of the shaft 5 and prevents their scoring the cylinder.

The cylinder has a by-pass l8 of such vertical extent as to span the upper set of rings Hi When the power piston is fully depressed. The sleevesection Ma is formed with an opening l9 which extends from above ports 25 in the body If! to a level at least approximating the top of the bypass when the power piston is fully elevated. At a point just above the fixed piston the cylinder has an intake port 2i with which a port 22, formed in the piston body It, is arranged to coincide when the power piston is fully elevated. There is a housing 23 projecting from the cylinder and having an extension 2G provided with a screw-cap 25 and the space thus formed communicates with the space 26 between the fixed piston and power piston head, forming therewith what I term the primary compression chamber. This chamber may be further enlarged, if desired, by extending the housing more or less around the cylinder, as at 23a. At a level to be just above the head of the power piston when fully depressed the cylinder has an exhaust port 21.

A spark plug is shown at 28.

Except as will be indicated and in a general way the operation is the same as is usual in this class of engines. On completion of each upstroke of the power piston a fuel charge previously admitted to the combustion chamber 29 is fired and a fresh fuel charge enters at 2l22 to the space 26. During the downstroke the latter charge is compressed in the said primary compression chamber and when the piston rings 56 are spanned by the by-pass such charge enters the combustion chamber, such occurring at about the time the power piston uncovers the exhaust port to permit the exploded charge to escape.

I have found in practice that, on account of varying conditions (for one example, in the quality of the fuel used) it becomes necessary in order to obtain the maximum eificiency in an engine of this class to make it possible to regulate the degree of primary compression effected with respect to each charge, i. e., the compression effected as an incident of the movement of the power piston toward the fixed piston. According to the invention, therefore, the space 26 has an extension forming the primary compression chamber and such chamber is provided with means, as the cap 25, for regulating its capacity and hence the degree of compression existing therein.

Referring, now, to Figs. 5 to 8, inclusive:

The crank-case 36, crank-shaft 3!, piston rod 32, cylinder 33, pin 3 power piston body 35 and its collar 38, fixed piston 37, exhaust port 38 and spark-plug 39 are or may be all substantially the same as already described.

A plate ii] corresponding to plate 6 here includes a housing divided horizontally into lower and upper chambers M and 52 by a partition t3, the lower chamber having an intake port lla, the upper chamber eduction ports 42a and the partition a port lSa. Port 43a is normally closed by a spring-urged valve M which may be opened by a cam Sla on the crank-shaft. The eduction ports lead to a circular port 44a concentric with the cylinder and with which angular ports 45 communicate. The angular ports communicate with the bores or ports of the (in this case) tubular standards 46 carrying the fixed piston. For convenience in manufacture the central part of the plate may be formed as a disk 41, the body portion (Fig. 7) of the plate being split and having an opening to receive the disk and provided with lugs and a bolt 48 connecting them whereby to clamp the disk in the opening, a further support being afforded by a flange 49 of the plate. However, it is not indispensable thus to form the plate in two parts.

Upstanding from the housing and communicating with chamber 42 is a tube 50 terminating at its upper end in a housing 5|, affording an outlet to the cylinder so that the passage 50a of the tube communicates with the cylinder at a level just above the power piston when fully depressed, such housing having an extension 52 provided with an adjustable cap 53.

The split sleeve 5% may be of the same construction and form as sleeve Mal4b without its opening is and is here held expanded against the cylinder by an elastic expansion element 55 having the same cross-section (see Fig. 4) as the rings l5 but itself shaped as a sleeve.

The operation in general is in this case as follows: On completion of the upstroke of the power piston a fuel charge previously admitted to the combustion chamber 55 is fired and a fresh fuel charge enters the space 57 between the two pistons via the ports lla-43a-42a and the tubular standards, cam Sla then opening valve M for this purpose and substantially at once allowing it to close. During the downstroke (valve M remaining closed) the latter charge is compressed in the primary compression chamber here afforded by space 51, the ports of the plate, chamber 42 and passage 50a, and when the power piston head clears the discharge end of said passage such charge enters the combustion chamher, the exploded charge escaping at the exhaust 38.

Here, again, the primary compression chamber is provided with means, as cap 53, for regulating the capacity of the extended primary compression chamber formed and hence the degree of compression existing in such chamber.

The split sleeve performs these important functions which in practice I find considerably increase the efficiency of an engine of this class: Heretofore there has been no provision for conserving the pressure developed during each primary compression (or here downward) movement of the power piston beyond forming such piston so that it would fit the cylinder as snugly as possible without undue binding and equipping it with upper and lower piston rings (as l6). Manifestly, the fit of the piston could not be so tight that there would not be some escape of the charge via the by-pass and thence around and between the piston and cylinder to the exhaust port 2i or 88; besides, wear has to be taken into account. When the split-sleeve is present, yieldingly held against the inside of the cylinder, it maintains such contact with the cylinder that at least with respect to the exhaust port a sleeve section as Mb hermetically seals that port at all times except at each instant when exhaust is to be eifected; in short, such section amounts to a valve. Further, in the construction according to Fig. 5, during the upstroke of the power piston the right-hand sleeve section acts as a valve with'respect to passage 50a, thereby conserving the vacuum in the primary compression chamber, and also preventing escape of the pressure in space 56 past the lower piston ring and to the crank case. Again, during compression of the charge in the combustion chamber 56 escape thereof past the upper piston rings (as l6) and thence to the exhaust port is prevented in the same way by the sleeve. While elastic devices, as the elastic rings I5 or the elastic sleeve 55, are desirable to maintain the split-sleeve in contact with the cylinder it is to be noted that the pressure of the charge finding its way between the power piston body and split-sleeve is active to the same end so that it tends to hold the sleeve in sliding contact with the cylinder; the split or splits in the split-sleeve permit any fluid seeking to pass around and between the cylinder and power piston body to enter between such body and the sleeve.

Referring, again, to Fig. 1: It is desired to avoid the formation of an excessive vacuum in and consequent possibility of leakage into the space, as 26, between the fixed piston and the head of the power piston structure on the upstrokes of the latter by preserving said space in communication with the mentioned extension thereof formed by parts 2324-25. If said structure were formed as usual, or so that when elevated it would lack the opening [9, this result might be accomplished by providing a vertical slot or slots in place of holes 20, except that then when said structure descends the slot would permit the developed pressure in said chamber to by-pass the fixed piston and escape to the atmosphere unless such piston were of undue vertical extent. internally to preserve a complete circumferential seal with the fixed piston throughout its whole effective vertical extent, but at the outside it is formed to preserve only asto the portion thereof which is below the by-pass (or remote from the closed end of the cylinder) a complete circumferential seal with the cylinder, above such portion affording a passage, as l9, whereby space 26 and its extension are united throughout substantially the full stroke of said structure.

Having thus fully described my invention what I claim is:

l. The combination, with fixed structure having a cylinder closed at one end and a fixed piston arranged within the cylinder and spaced from said end, a power piston in the cylinder having a piston head between said end and the fixed piston, instrumentalities for firing a fuel charge admitted to the space between said head and end when said head adjoins said end and for permitting exhaust from said space when said head approaches the fixed piston, said structure including a passage extending from the space between said piston head and fixed piston, and thence through the fixed piston from the space between the latter and said head and having an outlet to the interior of the cylinder at a point to be above the head when the latter adjoins the fixed piston and said structure also including a port to admit a fresh fuel charge to said passage, of a normally closed valve for said port and means driven by the power piston for controlling the valve.

2. The combination, with fixed structure having a cylinder closed at one end and a fixed piston arranged within the cylinder and spaced from said end, a power piston body in the cylinder having a piston head between said end and the fixed piston By my invention said structure is formed and a cylindrical skirt fitting between the fixed piston and cylinder, instrumentalities for admitting a fresh fuel charge to the space between said piston head and fixed piston and firing the charge in the space between said piston head and cylinder end when the head approaches the latter and for by-passing the fresh fuel charge from the firstto the second-named space when said head approaches the fixed piston, and an exhaust port in the cylinder arranged between said cylinder end and head and close to the latter when the same adjoins the fixed piston, of a valve for said port confined by said body to reciprocate therewith and against rotation around the same and arranged between said skirt and the cylinder at the side of the latter adjoining the port and normally held against the cylinder and formed to extend from approximately said head past the port when said head adjoins said cylinder end.

3. The combination, with fixed structure having a cylinder closed at one end and a fixed piston arranged within the cylinder and spaced from said end, a power piston body in the cylinder having a piston head between said end and the fixed piston and a cylindrical skirt fitting between the fixed piston and cylinder, instrumentalities for admitting a fresh fuel charge to the space between said piston head and fixed piston and firing the charge in the space between said piston head and cylinder end when the head approaches the latter and for Icy-passing the fresh fuel charge from the firstto the second-named space when said head approaches the fixed piston, and an exhaust port in the cylinder arranged between said cylinder end and head and close to the latter when the same adjoins the fixed piston, of a split sleeve confined by the power piston to reciprocate therewith and arranged between said skirt and the cylinder and normally held against the cylinder and formed to extend from approximately said head past the port when said head adjoins said cylinder end.

4. The combination, with fixed structure having a cylinder closed at one end and a fixed piston arranged within the cylinder and spaced from said end, a power piston body in the cylinder having a piston head between said end and the fixed piston and a cylindrical skirt fitting between the fixed piston and cylinder, and instrumentalities for firing a fuel charge admitted to the space between said head and end when said head adjoins said end and for permitting exhaust from said space when said head approaches the fixed piston, said structure including a passage extending through the fixed piston from the space between the latter and said head and having an outlet to the interior of the cylinder at a point above said head when the latter adjoins the fixed piston, of a valve for said outlet confined by the power piston body to reciprocate therewith and against rotation around the same and arranged between the skirt and the cylinder at the side of the latter adjoining said outlet and normally held against the cylinder and formed to extend from approximately said head past said passage when said head adjoins said cylinder end.

5. The combination, with fixed structure having a cylinder closed at one end and a fixed piston arranged within the cylinder and spaced from said end, a power piston structure in the cylinder having a piston head between said end and the fixed piston and a cylindrical skirt between the fixed piston and cylinder and formed interiorly to fit the latter, said fixed structure having a space communicating with the interior of the cylinder at a point between said end and the fixed piston and adapted to form with the space between said head and fixed piston structure a primary compression chamber affording a by-pass for fuel from the latter space to the space between said head and end, and instrumentalities for admitting a fresh fuel charge to said chamber and firing the charge in the last-named space when said head approaches said end and for permitting exhaust from said chamber when said head approaches the fixed piston, said power piston structure forming only a complete circumferential seal with the cylinder at the side of the by-pass remote from said end and its skirt having an exterior passage formed to reach from the first-named space to near said head when the the latter adjoins said end and near said head communicating with the second-narned space.

6. The combination, with fixed structure having a cylinder closed at one end and a fixed piston arranged within the cylinder and spaced from said end, a power piston body in the cylinder having a piston head between said end and the fixed piston and a cylindrical skirt fitting be tween the fixed piston and cylinder, instrumentalities for admitting a fresh fuel charge to the space between said piston head and fixed piston and firing the charge in the space between said piston head and cylinder end when the head approaches the latter and for by-passing the fresh fuel charge from the firstto the secondnamed space when said head approaches the fixed piston, and an exhaust port in the cylinder arranged between said cylinder end and head and lose to the latter when the same adjoins the fixed piston, of a part-cylindrical valve-device for said port concentric with the skirt of and confined by said body to reciprocate therewith and. against rotation around said body and arranged between the skirt and the cylinder at the side of the latter adjoining the port and normally held against the cylinder and formed to extend from approximately said head past the port when said head adjoins said cylinder end.

'7. The combination, with fixed structure having a cylinder closed at one end and a fixed piston arranged within the cylinder and spaced from said end, a power piston body in the cylinder having a piston head between said end and the fixed piston and a cylindrical skirt fitting between the fixed piston and cylinder, and instrumentalities for firing a fuel charge admitted to the space between said head and end when said head adjoins said end and for permitting exhaust from said space when said head approaches the fixed piston, said structure including a passage extending through the fixed piston from the space between the latter and said head and having an outlet to the interior of the cylinder at a point above said head when the latter adjoins the fixed piston, of a part-cylindrical valve-device for said outlet concentric with the skirt of and confined by said body to reciprocate therewith and against rotation around the same and arranged between the skirt and the cylinder at the side of the latter adjoining said outlet and normally held against the cylinder and formed to extend from approximately said head past said passage when said head adjoins said cylinder end.

GEORGE EXEL. 

